Schedule Value Project: Earned Value Management for Schedule Performance

PMBOK v8 Definition

Schedule performance index (SPI) is a measure of schedule efficiency expressed as the ratio of earned value to planned value. Schedule variance (SV) is a measure of schedule performance expressed as the difference between the earned value and the planned value. These metrics are calculated using the project schedule model, which is a representation of the plan for executing the project’s activities including durations, dependencies, and other planning information, used to produce a project schedule along with other scheduling artifacts.

Why It Matters for the Exam

Schedule value concepts (SPI and SV) appear frequently in PMI exam questions testing earned value management (EVM) calculations and interpretation. Questions typically present a scenario with EV, PV, and AC values, then ask you to calculate SPI or SV and determine whether the project is ahead of, on, or behind schedule. These questions are common in the "Monitor and Control" process group and the Schedule performance domain.

Key Points to Remember (for the exam)

• SPI Formula: SPI = EV / PV (Earned Value ÷ Planned Value)
• SV Formula: SV = EV - PV (Earned Value minus Planned Value)
• SPI Interpretation: SPI > 1.0 = ahead of schedule; SPI = 1.0 = on schedule; SPI < 1.0 = behind schedule
• SV Interpretation: SV > 0 = ahead of schedule; SV = 0 = on schedule; SV < 0 = behind schedule
• SPI is a ratio (efficiency measure); SV is a difference (variance measure)
• Common Confusion: SPI measures schedule efficiency, not cost efficiency (use CPI for cost)
• Schedule forecast predicts a timeline based on current progress, performance trends, and other information; forecasts are updated and reissued based on work performance obtained as the project is executed

Typical PMI Exam Example

A project has a planned value (PV) of $50,000 and an earned value (EV) of $40,000 at the data date. What is the schedule performance index (SPI) and what does it indicate?

Calculation: SPI = EV/PV = $40,000/$50,000 = 0.80. Since SPI < 1.0, the project is behind schedule, achieving only 80% of the planned progress.

PMI Exam Traps

• Trap: Confusing SPI with CPI (Cost Performance Index)

  • Reality: SPI = EV/PV (schedule); CPI = EV/AC (cost). They measure different performance dimensions.

• Trap: Thinking SV > 0 means under budget

  • Reality: SV > 0 means ahead of schedule. Cost variance (CV) = EV - AC measures budget performance.

• Trap: Interpreting SPI > 1.0 as "project is ahead of schedule" without considering the critical path

  • Reality: SPI measures overall schedule efficiency, but non-critical path activities may skew results. Always verify critical path status.

• Trap: Using actual duration instead of planned duration in schedule calculations

  • Reality: Actual duration is the time between actual start and data date; it is not used in SPI/SV calculations.

Important PMI Connections

Quick Review Questions

1. If EV = $75,000 and PV = $60,000, what is the SPI and what does it indicate about schedule performance?

2. A project has SPI = 0.85. Is the project ahead of, on, or behind schedule? What is the schedule efficiency percentage?

3. What is the difference between schedule variance (SV) and schedule performance index (SPI) in terms of what they measure?

4. A project manager calculates SV = -$10,000. What does this value tell you about the project's schedule status?

5. How does the schedule management plan relate to the calculation and interpretation of SPI and SV?

PMBOK v8 Reference

Section 2.3 - Schedule Performance Domain (as referenced in the provided context) and the definitions for schedule performance index (SPI) and schedule variance (SV) as provided in the PMBOK v8 glossary context.